When the balloon flies is dependant on the weather, best thing if you really want to go is take the opportunity whenever you see it open.
This is the info from the DLRP site.
Disneyland® Resort Paris seen from the top!
PANORAMAGIQUE: 100 000 passengers in the sky over Disneyland Resort Paris
Since the month of April 2005, Lake Disney at Disney Village has welcomed the «PanoraMagique» the largest captive balloon in the world that carries up to 30 passengers 100 meters above the ground.
The «PanoraMagique» has beaten all records of attendance with over 100 000 passengers by 31st of December, only nine months after its opening. It has become the most visited aerostat of all times and, given its success, will remain blown up all winter long.
This new attraction will offer our guests strong sensations during a six-minute ride up in the sky over Disneyland Resort Paris. As they rise 100 metres above the ground, guests will have a magnificent 360° wide and 20 kilometres long view, in one single glance. Up to thirty people can ride in the balloon at each ride (depending on the weather conditions).
Moored on Lake Disney at Disney Village, this giant helium-filled sphere will offer a unique and original trip with breathtaking and mind-blowing sensations!
Environmentally friendly and silent
High-performing (fast speed winch with 6 flights per hour)
Reliable (only system inthe world to be certified and approved as a Aéronef).
The price of the ticket will be 12 € per adult, 6 € per child from three to twelve years old and admission will be free for children under the age of three.